Characterization of pig tonsils as niches for the generation of Streptococcus suis diversity.

Streptococcus suis is a gram-positive bacterium that causes meningitis, septicemia, endocarditis, and other disorders in pigs and humans. We obtained 42 and 50 S. suis isolates from lesions of porcine endocarditis and palatine tonsils, respectively, of clinically healthy pigs in Japan; we then determined their sequence types (STs) by multilocus sequence typing (MLST), cps genotypes, serotypes, and presence of classical major virulence-associated marker genes (mrp, epf, and sly). The 42 isolates from endocarditis lesions were assigned to a limited number of STs and clonal complexes (CCs). On the other hand, the 50 isolates from tonsils were diverse in these traits and seemingly in the degree of virulence, suggesting that tonsils can accommodate a variety of S. suis isolates. The goeBURST full algorithm using tonsil isolates obtained in this study and those retrieved from the database showed that major CCs as well as many other clusters were composed of isolates originating from different countries, and some of the STs were very similar to each other despite the difference in country of origin. These findings indicate that S. suis with not only different but also similar mutations in the genome have survived in tonsils independently across different geographical locations. Therefore, unlike the lesions of endocarditis, the tonsils of pigs seemingly accommodate various S. suis lineages. The present study suggests that S. suis acquired its diversity by natural mutations during colonization and persistence in the tonsils of pigs.

Genetic characteristics of invasive pneumococcal disease-derived Streptococcus pneumoniae of serogroup 24 isolated in Tokyo, Japan.

BACKGROUND: Since the introduction of the national routine vaccination program against Streptococcus pneumoniae in Japan from the early 2010s, the incidence of invasive pneumococcal disease (IPD) caused by non-vaccine serotypes has increased. This study focused on non-vaccine serogroup 24 strains derived from IPD and aimed to clarify their genetic characteristics. METHODS: Between 2013 and 2022, 121 strains identified as serogroup 24 in patients with IPD were collected and applied to multilocus sequence typing and next-generation sequencing. Whole-genome data were used to delineate phylogenetic relationships and to identify virulence and antimicrobial resistance-associated genes. RESULTS: Recent trends in sequence types (STs) were characterized by an increase in the proportion of ST162 and ST2754 for 24F and 24B, respectively, after 2018. Whole-genome phylogenetic analysis demonstrated that serogroup 24 strains were organized into three clades, closely related to STs but not with serotypes. All ST162 strains were classified as Global Pneumococcal Sequence Cluster (GPSC) 6 and harbored the virulence-associated rlrA islet, with co-trimoxazole-resistance mutations in folA and folP genes. Two ST162 strains with different serotypes 24F and 24B from the same patient were phylogenetically indistinguishable, showing that these strains were derived by serotype conversion during infection. CONCLUSION: The recent changes in predominant STs were similar to those previously reported throughout Japan, except Tokyo. Little correlation between whole-genome phylogeny and serotypes and the observed serotype conversion in one patient indicate potentially variable immunogenicity of this serogroup.

Neisseria meningitidis serogroup W135 in a traveler visiting Japan from Argentina, 2019.

Invasive meningococcal disease (IMD) can occur in travelers returning from mass-gathering events or endemic regions. We present a 60-year-old Argentine traveler to Tokyo who developed IMD by Neisseria meningitidis Serogroup W135 during her stay in Japan. N. meningitidis serogroup W135 infection has become common in Argentina, whereas IMD less commonly occurs in Japan. Considering the prevalence, the patient most likely acquired the infection in Argentina, and it developed in Japan. Air travel enables passengers to reach the four corners of the world within a few days. IMD should be considered in travelers due to its potential to induce rapid clinical deterioration and transmission.

FRI-4 carbapenemase-producing Enterobacter cloacae complex isolated in Tokyo, Japan.

Objectives: A carbapenem-resistant Enterobacter cloacae complex isolated in Tokyo, Japan, produced a carbapenemase that was detected by a Carba NP test and a modified carbapenem inactivation method, but none of the 'Big Five' carbapenemase genes was detected by PCR. This study aimed to identify the carbapenemase. Methods: Carbapenemase genes were screened by WGS. Next, we generated a recombinant plasmid in which the carbapenemase gene was inserted. We also extracted the carbapenemase gene-carrying plasmid from the E. cloacae complex. The effects of both plasmids on the antibiotic susceptibility of Escherichia coli were then tested. The carbapenemase gene-carrying plasmid in the E. cloacae complex was completely sequenced. Results: A novel carbapenemase gene, blaFRI-4, encoded an amino acid sequence that was 93.2% identical to French imipenemase (FRI-1). E. coli transformed with blaFRI-4 showed reduced carbapenem susceptibility. A complete sequence of the blaFRI-4-carrying 98 508 bp IncFII/IncR plasmid (pTMTA61661) showed that blaFRI-4 and the surrounding region (18.7 kb) were duplicated. Conclusions: The FRI-4-producing E. cloacae complex was isolated in Japan, whereas all other FRI variants have been found in Europe, suggesting that the spread of FRI carbapenemases is global.

Non-serogroupable Neisseria meningitidis pneumonia in an immunocompetent patient with severe COVID-19 pneumonia: A case report.

Background: Non-serogroupable Neisseria meningitidis (N. meningitidis), the most common type of N. meningitidis in asymptomatic carriers, rarely causes infections. Most reported cases of infection are in patients with immunodeficiency, primarily complement deficiencies. Case presentation: A 54-year-old immunocompetent man was transferred to our hospital to treat severe coronavirus disease 2019 (COVID-19). The patient presented with cough producing a large amount of purulent sputum, which was considered an atypical presentation of COVID-19. Gram staining of the sputum revealed a large number of gram-negative diplococci phagocytosed by many neutrophils, and a diagnosis of bacterial pneumonia was established. The culture yielded non-serogroupable N. meningitidis, and the patient was diagnosed with non-serogroupable N. meningitidis pneumonia. Potential immunodeficiency was considered; however, testing including human immunodeficiency virus and complement factors showed no abnormalities. Conclusions: We report herein a rare case of non-serogroupable N. meningitidis pneumonia that occurred in an immunocompetent patient during the course of severe COVID-19. We consider impaired T cell function attributable to COVID-19 and dexamethasone administration may have triggered a transient immunosuppressive state and led to non-serogroupable N. meningitidis pneumonia.

Emergence of Phytobacter diazotrophicus carrying an IncA/C2 plasmid harboring bla NDM-1 in Tokyo, Japan.

Phytobacter diazotrophicus is an Enterobacterales species that was originally identified as a plant growth-promoting, Gram-negative bacterium. Recently, this species has been recognized as relevant to opportunistic human and nosocomial infections in clinical settings. Its frequent misidentification as other Enterobacterales species from clinical examination occasionally causes a delay in the identification of nosocomial outbreaks. Here, we report the emergence of New Delhi metallo-ß-lactamase (NDM)-producing P. diazotrophicus isolated from hospitalized pediatric patients and hospital environments in Tokyo, Japan. In our case, these isolates were found during an investigation of carbapenem-resistant Enterobacterales in relation to nosocomial infections. Whole-genome sequencing is useful for overcoming the difficulty of species identification. Furthermore, we found that bla NDM-1 was carried by an IncA/C2 plasmid (approximately 170 kbp), which was transferrable from the clinical isolates to the recipient strain Escherichia coli J53. Our study demonstrated that P. diazotrophicus behaves as a carrier of bla NDM-harboring plasmids, potentially disseminating resistance to carbapenems among Enterobacterales. IMPORTANCE Early detection of nosocomial outbreaks is important to minimize the spread of bacteria. When an outbreak is caused by multidrug-resistant bacteria such as carbapenem-resistant Enterobacterales, a delay in findings makes it difficult to control it because such bacteria often spread not only among human patients but also in hospital environments. Phytobacter diazotrophicus, an Enterobacterales species that has recently been found to be relevant to clinical settings, is often misidentified as other bacteria in clinical laboratories. Here, we found NDM-producing P. diazotrophicus in hospitalized pediatric patients and their environment in Tokyo, Japan. Given that the isolates carried bla NDM-1-harboring transferrable plasmids, the influence of such bacteria could be greater with the mediation of horizontal transfer of carbapenem resistance. Our findings suggest that P. diazotrophicus should be recognized as an NDM-carrier, for which more attention should be paid in clinical settings.

Molecular Characterization of blaNDM-Carrying IncX3 Plasmids: blaNDM-16b Likely Emerged from a Mutation of blaNDM-5 on IncX3 Plasmid.

Dissemination of blaNDM, which is carried on the IncX3 plasmid, among Enterobacterales has been reported worldwide. In particular, blaNDM-5-carrying IncX3 plasmids can spread among several hosts, facilitating their dissemination. Other variants, such as blaNDM-17-, blaNDM-19-, blaNDM-20-, blaNDM-21-, and blaNDM-33-carrying IncX3 plasmids, have also been reported. Here, we characterized, using whole-genome sequencing (WGS), a blaNDM-16b-carrying IncX3 plasmid harbored by Escherichia coli strain TA8571, which was isolated from a urine specimen of a hospital inpatient in Tokyo, Japan. The blaNDM-16b differed in sequence from blaNDM-5 (C > T at site 698, resulting in an Ala233Val substitution). This blaNDM-16b-carrying IncX3 plasmid (pTMTA8571-1) is 46,161 bp in length and transferred via conjugation. Transconjugants showed high resistance to ß-lactam antimicrobials (except for aztreonam). Because pTMTA8571-1, which carries the Tn125-related region containing blaNDM and conjugative transfer genes, was similar to the previously reported IncX3 plasmids, we performed phylogenetic analysis based on the sequence of 34 shared genes in 142 blaNDM-carrying IncX3 plasmids (22,846/46,923 bp). Comparative analysis of the shared genes revealed short branches on the phylogenetic tree (average of 1.08 nucleotide substitutions per shared genes), but each blaNDM variant was divided into separate groups, and the structure of the tree correlated with the flowchart of blaNDM nucleotide substitutions. The blaNDM-carrying IncX3 plasmids may thereby have evolved from the same ancestral plasmid with subsequent mutation of the blaNDM. Therefore, pTMTA8571-1 likely emerged from a blaNDM-5-carrying IncX3 plasmid. This study suggested that the spread of blaNDM-carrying IncX3 plasmids may be a hotbed for the emergence of novel variants of blaNDM. IMPORTANCE blaNDM-carrying IncX3 plasmids have been reported worldwide. Harbored blaNDM variants were mainly blaNDM-5, but there were also rare variants like blaNDM-17, blaNDM-19, blaNDM-20, blaNDM-21, and blaNDM-33, including blaNDM-16b detected in this study. For these plasmids, previous reports analyzed whole genomes or parts of sequences among a small number of samples, whereas, in this study, we performed an analysis of 142 blaNDM-carrying IncX3 plasmids detected around the world. The results showed that regardless of the blaNDM variants, blaNDM-carrying IncX3 plasmids harbored highly similar shared genes. Because these plasmids already spread worldwide may be a hotbed for the emergence of rare or novel variants of blaNDM, increased attention should be paid to blaNDM-carrying IncX3 plasmids in the future.

Multiple ß-Lactam Resistance Gene-Carrying Plasmid Harbored by Klebsiella quasipneumoniae Isolated from Urban Sewage in Japan.

The continuous emergence of carbapenemase-producing Enterobacteriaceae (CPE) presents a great public health challenge. Mitigation of CPE spread in the environment is crucial, particularly from a One Health perspective. Here we describe the isolation of CPE strain SNI47 from influent water of a sewage treatment plant in Japan. SNI47 was identified as Klebsiella quasipneumoniae subsp. quasipneumoniae by phylogenetic analysis and was resistant to ß-lactams, including carbapenems. Of four plasmids detected from SNI47, the 185,311-bp IncA/C2 plasmid (pTMSNI47-1), which carried 10 drug resistance genes, including genes for four ß-lactamases (blaCTX-M-2, blaDHA-1, blaKHM-1, and blaOXA-10), was transferred to Escherichia coli J53 via conjugation. The MICs of all tested ß-lactams for the transconjugant were higher than for the recipient. We constructed recombinant plasmids, into which each ß-lactamase gene was inserted, and used them to transform E. coli DH5α cells, demonstrating that KHM-1 enhanced carbapenem resistance. In addition, these ß-lactamases were responsible for a wide-spectrum ß-lactam resistance acquisition with mutual compensation. KHM-1, recognized as a rare type of metallo-ß-lactamase, was detected in a transferable plasmid, from a sewage treatment plant, involved in horizontal gene transfer. The detection of such plasmids raises a health risk alarm for CPE dissemination.IMPORTANCE In our investigation of urban wastewater in Japan, carbapenem-resistant Klebsiella quasipneumoniae subsp. quasipneumoniae was isolated that carried the pTMSNI47-1 plasmid, which carries four ß-lactamase genes and has transferability among Enterobacteriaceae pTMSNI47-1 was found to encode a rarely reported carbapenemase, KHM-1. Cooperative effects of ß-lactamases encoded by pTMSNI47-1 appeared to have broad-spectrum resistance to ß-lactams. The detection of the KHM-1 gene in urban wastewater suggests that such a rare antimicrobial resistance (AMR) gene can be pooled in the environment, potentially emerging as an AMR determinant in a pathogen. When the number of ß-lactamase resistance genes is increased in one plasmid, the transfer of this plasmid can confer broad-spectrum resistance to ß-lactams, even if the individual gene confers narrow-spectrum resistance. The present study adds important information about the potential risk of sewage treatment plants as reservoirs and environmental suppliers of AMR genes, contributing to the public health from a One Health perspective.

IMP-68, a Novel IMP-Type Metallo-ß-Lactamase in Imipenem-Susceptible Klebsiella pneumoniae.

We recently detected a novel variant of an IMP-type metallo-ß-lactamase gene (blaIMP-68) from meropenem-resistant but imipenem-susceptible Klebsiella pneumoniae TA6363 isolated in Tokyo, Japan. blaIMP-68 encodes a Ser262Gly point mutant of IMP-11, and transformation experiments showed that blaIMP-68 increased the MIC of carbapenems in recipient strains, whereas the MIC of imipenem was not greatly increased relative to that of other carbapenems, including meropenem. Kinetics experiments showed that IMP-68 imipenem-hydrolyzing activity was lower than that for other carbapenems, suggesting that the antimicrobial susceptibility profile of TA6363 originated from IMP-68 substrate specificity. Whole-genome sequencing showed that blaIMP-68 is harbored by the class 1 integron located on the IncL/M plasmid pTMTA63632 (88,953 bp), which was transferable via conjugation. The presence of plasmid-borne blaIMP-68 is notable, because it conferred antimicrobial resistance to carbapenems, except for imipenem, on Enterobacteriaceae and will likely affect treatment plans using antibacterial agents in clinical settings.IMPORTANCE IMP-type metallo-ß-lactamases comprise one group of the "Big 5" carbapenemases. Here, a novel blaIMP-68 gene encoding IMP-68 (harboring a Ser262Gly point mutant of IMP-11) was discovered from meropenem-resistant but imipenem-susceptible Klebsiella pneumoniae TA6363. The Ser262Gly substitution was previously identified as important for substrate specificity according to a study of other IMP variants, including IMP-6. We confirmed that IMP-68 exhibited weaker imipenem-hydrolyzing activity than that for other carbapenems, demonstrating that the antimicrobial susceptibility profile of TA6363 originated from IMP-68 substrate specificity, with this likely to affect treatment strategies using antibacterial agents in clinical settings. Notably, the carbapenem resistance conferred by IMP-68 was undetectable based on the MIC of imipenem as a carbapenem representative, which demonstrates a comparable antimicrobial susceptibility profile to IMP-6-producing Enterobacteriaceae that previously spread in Japan due to lack of awareness of its existence.